TiC MR-head magnetic shield dummy shield spark gap

ABSTRACT

A magneto-resistive read head having a &#34;parasitic shield&#34; provides an alternative path for currents associated with sparkovers, thus preventing such currents from damaging the read head. The parasitic shield is provided in close proximity to a conventional magnetic shield. The electrical potential of parasitic shield is held essentially equal to the electrical potential of the sensor element. If charges accumulate on the conventional shield, current will flow to the parasitic shield at a lower potential than would be required for current to flow between the conventional shield and the sensor element. Alternatively, conductive spark gap devices are electrically coupled to sensor element leads and to each magnetic shield. Each spark gap device is brought within very close proximity of the substrate to provide an alternative path for charge that builds up between the sensor element and the substrate to be discharged. The ends of the spark gaps that are brought into close proximity of the substrate are preferably configured with high electric field density inducing structures which reduce the voltage required to cause a sparkover between the spark gap device and the substrate.

This application is a division of application Ser. No. 08/480,069, filedon Jun. 7, 1995, U.S. Pat. No. 5,761,009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to read heads for computer datastorage devices. In particular, the invention concerns a structure forprotecting a read head from electrostatic discharge.

2. Description of the Related Art

Data storage devices, such as magnetic disk drives and tape drives, usedto store information for computer systems are well known. In magneticdata storage devices, a medium, such as a magnetic disk platter ormagnetic tape, is treated with magnetic material. The magnetic materialcan be polarized in order to cause phase reversals in a magnetic fieldto encode information on the medium. The phase reversals used to encodeinformation can be detected by magnetic sensors, commonly referred to asread heads. It is common for a read head to be mounted in a structure,commonly referred to as a slider. Sliders typically fly over the surfaceof the medium supported by a thin layer of air, commonly referred to asan air bearing. The air bearing is generated by relative motion of theslider with respect to the medium. For example, in a disk drive device,the disk platter is rotated to generate relative motion between themedium and the slider. The slider may be positioned radially over themedium to allow the read head access to any region of the medium as themedium rotates. FIG. 1 is an illustration of a slider 1 having two rails3. Each rail 3 has an air bearing surface 5. A read head 7 is located ona "deposition end" 4 of each rail. The slider 1 moves in the directionof arrow 9 relative to a magnetic medium.

One well known type of read head is referred to as a magneto-resistive("MR") head. An MR head uses magneto-resistive material (commonlyreferred to as an "MR sensor element") to sense changes in a localmagnetic field. FIG. 2 is a simplified illustration of a cross-sectionof an M read head 7 within a rail 3 of a slider 1, viewed from the airbearing surface 5. The arrow 9 indicates the direction of the read head7 with respect to the medium over which the read head 7 flies. An MRsensor element 11 is shown disposed between a first magnetic shield 13and a second magnetic shield 15. The first and second shields 13, 15 aretypically formed of a magnetic material, such as a nickel/iron alloy,which prevents the magnetic fields of adjacent regions of the mediumfrom distorting the fields associated with the information that is beingread from the medium. Surrounding each shield 13, 15 and the MR sensorelement 11 is an insulating material 17, such as alumina. The insulator17 prevents the MR sensor element 11 from coming into direct electricalcontact with either the first or second shield 13, 15. Also shown inFIG. 2 is a substrate 19. The substrate 19 may be a ceramic material,such as titanium carbide.

FIG. 3 is a cross-sectional view through line 3--3 of the read head 7shown in FIG. 2. The MR sensor element 11 (shown by broken line toindicate that the sensor 11 is obscured by a sensor lead 21) is coupledto additional circuitry, which is well known in the art, by sensor leads21 (only one such lead 21 is shown on the near side of the MR sensorelement 11). A second lead (not shown) is coupled to another side of theMR sensor element 11. A carbon overcoat 20 may be applied to the airbearing surface 5 to minimize wear and protect the relatively softshields 13, 15 and MR sensor element 11 from damage. The overcoat 20 haslittle effect on the likelihood that a sparkover will occur at the airbearing surface 5.

One problem with MR heads, such as the head 7 shown in FIGS. 1-3 is thatelectrostatic charges may be transferred from an external source (suchas a human body) to the components of the MR read head 7 (such as theshields 13, 15, MR sensor element 11, and substrate 19) duringproduction. When the charge transferred to one component is sufficientlylarge, an electrical discharge, commonly referred to as a "sparkover"occurs. Such sparkovers are most likely to occur during production andhandling of the head 7.

Sparkovers can damage the head. For example, the high current density atthe sparkover location typically results in material near the sparkovermelting. This damage may occur at the air bearing surface 5 of theslider 1. In a high percentage of MR read heads in which sparkoverdamage at the air bearing surface 5 occurs, the result of the sparkoverdamage is either increased resistance, or alternatively, a near opencircuit condition in the MR sensor element circuit. In addition, damageto the air bearing surface 5 results in undesirable changes in theflying height characteristics of the slider 1. That is, even the minorchanges in the surface characteristics of the air bearing surface 5 havea great impact on the flying height characteristics of the slider 1.Because of the undesirable effects of sparkovers, the manufacturingyield for MR read heads is reduced in proportion to the frequency withwhich such sparkovers typically occur.

Studies of such electrostatic discharges have revealed that thesedischarges typically occur in one of three regions. These three regionsare indicated in FIG. 3 by the letters "A", "B", and "C". As shown inFIG. 3, the regions of discharge are typically along the air bearingsurface 5 (even when a carbon overcoat 20 is provided) due to a higherelectric field generated in the air bearing.

FIG. 4 illustrates an electrical model of the circuit formed by theelements of the MR head 7. The resistance of the leads 21 to and fromthe MR sensor element 11 is modeled as two resistors 23, 24. Theresistance of the MR sensor element 11 is modeled as a resistor 25. Onemethod for preventing damage due to electrostatic discharge is taught byU.S. Pat. No. 5,272,582, entitled "Magneto-Resistance Effect MagneticHead with Static Electricity Protection", issued to Shibata, et. al onDec. 21, 1993. In Shibata, two sensor element magnetic cores aredeposited to form a magnetic gap near the air bearing surface of aslider. The two magnetic cores are in magnetic contact with one anotherat a "back gap" which is away from the magnetic gap. An insulating layeris placed between each sensor element magnetic core at the magnetic gap.An MR sensor element is place between the insulating layers such thatthe MR sensor element is within the magnetic gap. A ground conductivelayer is electrically connected to a first of the magnetic cores toroute to ground the electric charges coming into the magnetic gap fromthe magnetic recording medium. Accordingly, Shibata attempts to keep themagnetic cores which form the magnetic gap at a controlled potential.This arrangement is intended to prevent electric charges that may comefrom the magnetic recording medium from rushing into the magnetic gap.

A second method for preventing electro-static discharge and theassociated damage that such discharge causes is taught in IBM TechnicalDisclosure Bulletin, Vol. 21, No. 11, dated Apr., 1979, by Rohen(hereinafter referred to as "Rohen"). FIG. 5 illustrates the approachtaken by Rohen. In FIG. 5, an MR element 31 is located at one end of thestructure. A first conductive region 33 and a second conductive region35 are electrically coupled to a ground potential via terminals 37, 39.An insulating material 41 isolates these regions 31, 33 from twoadditional conductive regions 43, 45. Regions 43, 45 provide aconductive path for current to the MR element 31. During fabrication,the upper portion 47 of the structure is removed to the broken line 49.By coupling the regions 33, 35 to a ground potential, a low potentialpoint is provided for any direct electrostatic discharges, and thegrounded side bars formed by the regions 33, 35 provide a Faraday shieldto lessen the effect of indirect electrostatic discharges.

A third method for preventing electrostatic discharge and the associateddamage that such discharge causes, requires providing an alternativepath for a sparkover. This method has been used with conventionalinductive read/write heads. For example, in a typical inductiveread/write head, the inductive coil is greater than approximately 3 μmfrom the yoke. The dielectric between the inductive coil and the yoke istypically an insulator, such as alumina (A1₂ O₃). A spark gap device isformed which causes a sparkover from the inductive coil or the yoke inorder to reduce any electro-static charge that builds on thesecomponents. Such a spark gap device is placed close to a component to bedischarged. The charge built up on the component will cause a sparkoverto the spark gap device at a lower voltage than is required to cause asparkover to any other component. For example, in a conventionalinductive read/write head, a spark gap device would be locatedapproximately 1 μm from the component to be discharged. Thus, asparkover will occur at a substantially lower voltage than is requiredfor a sparkover across the 3 μm gap between the yoke and inductive coil.

However, because of the relatively short distance between the componentsof an MR read head, the voltage at which a sparkover occurs betweenthose components is relatively low. For example, the voltage required tocause a sparkover (i.e., the "sparkover voltage") between an MR sensorlead and a grounded magnetic shield separated by 0.12 μm is only 60volts.

In contrast, in a typical MR head (such as the head 7 shown in FIG. 1)the distance between one of the magnetic shields 13, 15 and the MRsensor element 11 is approximately 0.12 μm. Therefore, a sparkover willoccur between the magnetic shields 13, 15 and MR sensor element 11 of aconventional MR read head at a far lower voltage than between the yokeand inductive coil in a conventional inductive read/write head.Furthermore, because the sparkover between components of the MR readhead 7 can occur though air at the air bearing surface, the requiredsparkover voltage between the magnetic shields 13, 15 and the MR sensorelement 11 is even lower than would be the case if the sparkover had totraverse an insulator. Accordingly, it would be very difficult todevelop a spark gap device which would provide an alternative path fordischarge of any charge that builds on the components of an MR read head(i.e., a path through which a sparkover can be induced by a weakerelectric field than is required to cause a sparkover between thecomponents of the MR read head). For example, voltages in excess of 1000volts are required to cause a sparkover between a yoke and inductivecoil in a conventional inductive device. In contrast, 60 volts can causea sparkover between an MR sensor lead and a grounded magnetic shieldseparated by 0.12 μm. This difference is due to the relatively shortdistance across the gap between the MR sensor lead and the magneticshield, and also due to the fact that the components of an MR read headare essentially exposed to air at the air bearing surface. Thedielectric constant for air is such that sparkover will occur at lowervoltages across air than across many other materials.

While the solutions provided by Rohen and Shibata reduce the chance ofdamage to an MR read head occurring, damage due to sparkovers(particularly at the air bearing surface) remain a persistent problemwhich undesirably effects manufacturing yield. Accordingly, it is anobject of the present invention to provide a structure that is lesssusceptible to harmful sparkovers at the air bearing surface. Anotherobject of the present invention is to provide an inexpensive structurewhich is less susceptible to damage from sparkovers at the air bearingsurface. Still another object of the present invention is to provide amethod for efficiently fabricating a structure that is less susceptibleto damage from sparkovers at the air bearing surface.

SUMMARY OF THE INVENTION

The present invention is a magneto-resistive read head used to sensemagnetic fields which emanate from a magnetic storage medium, such as aplatter of a computer disk drive device or magnetic tape used in a tapedrive. In accordance with one embodiment of the present invention,"parasitic shields" are placed in close proximity to magnetic shields ofa read head. The gap between a parasitic shield and a magnetic shield ispreferably narrower than the gap between a magnetic shield and eitherthe substrate on which the read head is formed, or a sensor element.Accordingly, a parasitic shield provides an alternative path forcurrents associated with sparkovers, thus preventing such currents fromdamaging the read head.

Each of the parasitic shields is electrically coupled to the sensorelement through a resistive element. Therefore, the electrical potentialof parasitic shield will be essentially equal to the electricalpotential of the sensor element. Accordingly, if charges accumulate onthe magnetic shield, current will flow to the parasitic shield at alower potential than would be required for current to flow between themagnetic shield and the sensor element. Alternatively, the parasiticshields may be directly electrically coupled to a structure of knownelectrical potential, such as the substrate.

In accordance with a second embodiment of the present invention,conductive spark gap devices are electrically coupled to sensor elementleads and to each magnetic shield. Each spark gap device is brought intovery close proximity of the substrate to provide an alternative path forcharges that build up between the sensor element and the substrate to bedischarged. In accordance with one embodiment of the present invention,the spark gap devices are fabricated at the wafer level on a depositionend of a wafer of semiconductor substrate material usingphotolithography and masking techniques. In one embodiment of thepresent invention, pads at the deposition end may be connected to thesubstrate and shields to allow external connections to be made.

In the preferred embodiment of the present invention, the ends of thespark gaps that are brought into close proximity with the substrate areconfigured with high electric field density inducing structures whichreduce the voltage required to cause a sparkover between the spark gapdevice and the substrate. Alternatively, the spark gap devices may bedirectly coupled to the substrate and brought into close proximity withthe magnetic shields and the sensor element.

The details of the present invention, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a prior art slider used in aconventional computer disk drive device;

FIG. 2 is a partial cross-sectional view of a prior art MR read head,viewed from the air bearing surface;

FIG. 3 is a partial cross-sectional view of a prior art MR read headtaken along line 3--3 of FIG. 2;

FIG. 4 is a model of the electrical circuit formed by the prior art MRhead shown in FIGS. 2 and 3;

FIG. 5 is an illustration of a prior art MR head with grounded sidebars;

FIG. 6a is a partial cross-sectional view of an MR read head inaccordance with one embodiment of the present invention;

FIG. 6b is a partial cross-sectional view of an MR read head inaccordance with another embodiment of the present invention;

FIG. 6c is a cross-sectional view of the inventive read head taken alongthe line 6c-6c of FIG. 6a;

FIG. 7a and 7b are models of the electrical circuit formed by theinventive MR head shown in FIGS. 6a-6c;

FIG. 8 illustrates one fabrication process in accordance with the firstembodiment of the present invention;

FIGS. 9A and 9B is a flowchart of the process steps performed in theinventive method;

FIGS. 10-16 illustrate additional steps performed in accordance with themethod of the present invention;

FIG. 17 is an illustration of a second embodiment of the presentinvention;

FIG. 18a is an illustration of an embodiment of the present inventionusing a conductive stud to attract sparkovers;

FIG. 18b is a cross-sectional view of the embodiment of the presentinvention taken along the line 18b--18b of FIG. 18a.

FIG. 19 is an illustration of one embodiment of the present invention inwhich a pad which connects the sensor element to circuitry outside theread head is shown.

FIG. 20 is a deposition end view of another embodiment of the presentinvention in which each shield is also electrically coupled to a pad atthe deposition end of a read head.

FIG. 21a and 21b are flowcharts of the method of fabricating the readhead of FIG. 18a in accordance with one embodiment of the presentinvention.

FIG. 22 is a magnetic disk storage system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 22 is a magnetic disk storage system. It will be apparent to one ofordinary skill that the present invention, while described as being foruse in a magnetic disk storage system, may be used in any data storagesystem in which the inventive head is used, such as magnetic taperecording systems, etc. At least one rotatable magnetic disk 2212 issupported on a spindle 2214 and rotated by a disk drive motor 2218. Themagnetic recording media on each disk is in the form of an annularpattern of concentric data tracks (not shown) on the disk 2212. At leastone slider 2213 is positioned on the disk 2212, each slider 2213supporting one or more magnetic read/write transducers 2221, typicallyreferred to as read/write heads. As the disks rotate, the sliders 2213are moved radially in and out over the disk surface 2222 so that theheads 2221 may access different portions of the disk where desired datais recorded. Each slider 2213 is attached to an actuator arm 2219 bymeans of a suspension 2215. The suspension 2215 provides a slight springforce which biases the slider 2213 against the disk surface 2222. Eachactuator arm 2219 is attached to an actuator means 2227. The actuatormeans as shown in FIG. 22 may be a voice coil motor (VCM), for example.The VCM comprises a coil moveable within a fixed magnetic field, thedirection and velocity of the coil movements being controlled by themotor current signals supplied by a controller.

During operation of the disk storage system, the rotation of the disk2212 generates an air bearing between the slider 2213 and the disksurface 2222 which exerts an upward force (i.e., lift) on the slider.The air bearing thus counterbalances the slight spring force of thesuspension 2215 and supports the slider 2213 off and slightly above thedisk surface by a small, substantially constant spacing duringoperation.

The various components of the disk storage system are controlled inoperation by control signal generated by control unit 2229, such asaccess control signals and internal clock signals. Typically, thecontrol unit 2229 comprises logic control circuits, storage means and amicroprocessor, for example. The control unit 2229 generates controlsignals to control various system operations such as drive motor controlsignals on line 2223 and head position and seek control signals on line2228. The control signals on line 2228 provide the desired currentprofiles to optimally move and position a selected slider 2213 to thedesired data track on the associated disk 2212. Read and write signalsare communicate to and from read/write heads 2221 by means of recordingchannel 2225.

The above description of a typical magnetic disk storage system, and theaccompanying illustration of FIG. 22, are provided only as oneillustration of the present invention. It should be apparent that diskstorage systems may contain a large number of disks and actuators, andeach actuator may support a number of sliders.

FIG. 6a is a partial cross-sectional view of a magneto-resistive ("MR")read head 107 in accordance with a first embodiment of the presentinvention. The MR read head 107 of FIG. 6a is fabricated on a substrate119. The substrate 119 may be fabricated from any suitable conventionalmaterial used to fabricate sliders, such as titanium carbide ceramic. Itwill be understood by those of ordinary skill in the art that theparticular substrate material is not essential to the present invention.For example, in an alternative embodiment of the present invention, thesubstrate may be either a conductive material (such as ferrite, orferrite composition), semiconductor material (such as silicon singlecrystal), or insulating material (such as alumina). The MR read head 107includes a first magnetic shield 113, a second magnetic shield 115, asensor element 111, four parasitic shields 124, each parasitic shield124 formed in close proximity to one of the magnetic shields 113, 115.

In one embodiment of the present invention, shown in FIG. 6a, theproximal end 127 of each parasitic shield 124 generally conforms to theshape of the nearby end of the magnetic shield 113, 115. Alternatively,the proximal end 127 of each parasitic shield 124 may have high electricfield density inducing structures (HEFDI structures). For example, asshown in FIG. 6b, the proximal end 127 of each parasitic shield 124 maybe formed with one or more HEDFI structures, such as a generally pointedstructure (i.e., structure preferably with a radius of less than about 1μm) which causes the electric field intensity to be concentrated. Itwill be understood by those skilled in the art, that structures withradii of greater than 1 μm may be used. However, the smaller the radius,the greater the concentration of charge. Due to the concentration ofelectric fields in the HEFDI structures, the likelihood of a sparkoverbetween a parasitic shield 124 and a magnetic shield 113, 115 increases.Accordingly, sparkovers are less likely to occur between the magneticshield 113, 115 and either the sensor element 111 or between themagnetic shield 113, 115 and the substrate 119. A single HEFDI structuremay be provided. However, a plurality of such HEFDI structures arepreferable, since a high current density sparkover may distort a singleHEFDI structure, thereby reducing the ability of the HEFDI toconcentrate the electric field. By having more than one such HEFDIstructure, occurrence of more than one high current sparkover through aHEFDI structure will be possible, even if the sparkover causes damage tothe structure through which current flows. A tradeoff between spaceavailable in the read head and the number of HEFDI structures requiresthat the particular preferred number of HEFDI structures be selectedafter consideration of the dimensions of the read head and thelikelihood of multiple sparkovers.

FIG. 6b illustrates an alternative embodiment in which a special pad 170is electrically coupled to the magnetic shield 115 by a conductiveelement 171. Additional conductive elements (not shown) may be used toelectrically couple other components of the read head 107 to additionalpads (not shown) in similar fashion.

FIG. 6c is a cross-sectional view of the read head 107 taken along theline 6c--6c of FIG. 6a. FIG. 6c reveals that the parasitic shields 124do not extend near the air bearing surface 5. By forming the parasiticshields 124 well above the air bearing surface (i.e., preferably abouttwice the distance between the parasitic shield 124 and the magneticshield 115) the chance that a sparkover will occur at the air bearingsurface is substantially reduced.

In one embodiment of the present invention, each magnetic shield 113,115 is fabricated from a nickel/iron alloy, commonly known as permalloy.Alternatively, the magnetic shields 113, 115 may be fabricated from anyrelatively permeable material (such as ferrite). In the preferredembodiment of the present invention, the parasitic shields 124 arefabricated from the same material as the magnetic shields 113, 115 toallow at least one parasitic shield to be formed by the same processstep which forms a magnetic shield. Alternatively, the parasitic shields124 may be fabricated from any conductive material.

The parasitic shields 124 are preferably electrically coupled to thesensor element through a conduction path. In one embodiment of thepresent invention, approximately 10-100 kilohms of resistance isprovided in the conductive path between each parasitic shield and one oftwo conventional sensor element 111 leads 21 (see FIG. 7a). The sensorelement leads 21 allow current to flow to and from the sensor element111. One of the sensor element leads 21 hides the sensor element 111 inFIG. 6c.The sensor element 111 is, therefore, illustrated by a brokenline.

A spark gap 125 exists between each of the magnetic shields 113, 115 andat least one of the parasitic shields 124. In the preferred embodiment,two spark gaps 125 are associated with each magnetic shield 113, 115,one on each side of each magnetic shield 113, 115. The spark gaps 125are preferably formed such that current will flow across the spark gaps125 before current flows between a magnetic shield 113, 115 and eitherthe sensor element 111 or the substrate 119. That is, the spark gaps 125are narrower than the gap between the sensor element 111 and themagnetic shields 113, 115. Accordingly, any sparkover that occurs due toexcessive charge that builds up between one of the magnetic shields 113,115 and the sensor element 111 will be discharged across the spark gap125 by a sparkover between the magnetic shield 113, 115 and one or bothof the associated parasitic shields 124.

FIG. 7a is a schematic of a model of the electrical characteristics ofthe first embodiment of the MR head 107 of the present invention. Eachof the magnetic shields 113, 115 are capacitively coupled to the sensorleads 21 by capacitors 132, 134, 136, and 138. Each of the capacitors132-138 represent the capacitance between the shields 113, 115 and thesensor leads 21. For example, capacitor 132 represents the capacitancethat exists due to the proximity of the magnetic shield 113 to thesensor lead 21. In addition, a capacitor 168 represents the capacitancebetween the shield 113 and the substrate 119. An element 140, 142, 144and 146, such as resistor, diode metal oxide semiconductor field effecttransistor (MOSFET), or electrostatic discharge (ESD) circuit, iscoupled between each parasitic shield 124 and the sensor leads 21. Inone embodiment of the present invention, a resistor having a resistanceof approximately in the range of 10 kilohms to 100 kilohms is providedin series between the parasitic shield and the sensor element 111.Alternatively, the parasitic shield may be directly electrically coupledto a structure of known electric potential, such as the substrate.

Resistance in the sensor leads 21 due to the length of these leads isrepresented by resistors 150, 152. In addition, there is a capacitancethat exists between the sensor leads 21 and the substrate 119, which isrepresented by capacitors 154, 156. For the purpose of this discussion,the substrate 119 is considered to be at ground potential.

A capacitance, represented by capacitors 158, 160, 162, 164, also existsbetween each of the parasitic shields 124 and the adjacent sensor lead21. As charge accumulates on the magnetic shields 113, 115, the sameelectrical potential will exist between each of the parasitic shields124 and the magnetic shields 113, 115 that exists between the sensorelement 111 and the magnetic shields 113, 115. That is, any charge thatwould accumulate on the parasitic shields 124 will be distributed evenlythroughout the sensor element 111 and the parasitic shields 124 by theelements 140, 142, 144, 146. Accordingly, if the potential required tocause a sparkover through the gap 125 is less than the potentialrequired to cause a sparkover through the gap between any one of themagnetic shields 113, 115 and the sensor element 111, then no sparkoverwill ever occur between the magnetic shields 113, 115 and the sensorelement 111. That is, no harmful electro-static discharge will occurbetween the magnetic shields 113, 115 and the sensor element 111, sinceany charge that accumulates between the magnetic shields 113, 115 andthe sensor element 111 will be dissipated by a sparkover between thesensor element 111 and the parasitic shield 124 before it issufficiently great to cause a sparkover between the sensor element andthe magnetic shield. Since the spark gap 125 is not near the air bearingsurface 5, the result of a sparkover through the spark gap 125 will befar less disruptive to the operation of the read head 107.

In accordance with another embodiment of the present invention shown inFIG. 7b, a electro-static discharge circuit 166 is placed between atleast one of the magnetic shields 113, 115 and at least one of theparasitic shields 124. The electro-static discharge circuit 166 mayconsist of a single element, such as a P-channel MOSFET, N-channelMOSFET, or a thin film transistor (TFT). In one embodiment of theinvention, the gate of the transistor is coupled to either the drain orthe source. Alternatively, the gate is coupled to a control circuit,such as the MR circuit. Such a control circuit may then alter thecharacteristic of the electrostatic discharge circuit 166. In oneembodiment of the present invention, the drain is coupled to theparasitic shield 124 and the source is coupled to the magnetic shield113, 115. Alternatively, the source is coupled to the parasitic shield124 and the drain is coupled to the magnetic shield 113, 115.

FIG. 8 illustrates a first step in one fabrication process in accordancewith the first embodiment of the present invention. FIG. 9 is aflowchart of the process steps performed in the inventive method. Inaccordance with the embodiment illustrated in FIGS. 8, the MR read headis fabricated on a substrate 119. An insulator 117 (such as alumina) isapplied to a deposition end 121, such as by being deposited on thedeposition end 121 of the substrate 119 (STEP 901). Alternatively, theinsulator 117 may be applied by any well-known technique, such assputtering an insulting material, such as alumina on the substrate 119,introducing a liquid polymer onto the wafer and spinning the wafer todistribute the polymer, or depositing the insulating material by achemical vapor deposition (CVD) technique. "Spacer" structures (i.e.,spacers) are then formed. In one embodiment of the present invention,the spacers are formed in accordance with a technique disclosed in U.S.Pat. No. 4,256,514, entitled "Method Of Forming a Narrow DimensionedRegion on a Body", issued on Mar. 17, 1981 to Pogge, and assigned to theassignee of the present application. For example, in one embodiment ofthe present invention, a polysilicon "gate" 118 is applied to theinsulator 117 (such as by a conventional semiconductor depositiontechnique, and conventional photolithography technique or conventionalmasking technique) (STEP 903). The polysilicon gate is a platform (orstep) upon which additional structures may be formed. For example, alayer of material 120 (such as an oxide or nitride layer) is thenapplied over surfaces 114, 116 of the insulator 117 and the gate 118,such that at least a first and second external side wall 180, 182 and atop surface 184 are formed on the gate 118 in an essentially evencoating of the material 120 (STEP 905). The material 120 is preferablyselectively removable, such as being selectively etchable.

The material 120 is then preferably treated to essentially remove thematerial 120 that was applied over the insulator 120, leaving only thematerial 120 that is not coplanar with a plane that is parallel to theinterface between the insulator 117 and the substrate 119. For example,oxide may be selectively etched from the alumina and polysilicon withoutgreatly affecting either the alumina or the polysilicon by using anyconventional etching agent. After the selective removal, essentiallyonly the external side walls 180, 182 remain, as shown in FIG. 10 (STEP907). Next, another selective removal process is performed to remove thegate 118 (STEP 909), as shown in FIG. 11. Removal of the gate 118 leavestwo very narrow spacers 180, 182 of the material 120.

After forming the spacers, a magnetic material (such as nickel/ironpermalloy or sendust) is applied to form two parasitic shields 124 and afirst magnetic shield 113 (STEP 911) as shown in FIG. 12. Typically, theshields 124, 113 will extend above the spacers 180, 182. Therefore, inthe preferred embodiment, the shields 124, 1I3 are polished (i.e.,lapped) down to remove that portion of the shields 124, 113 that isabove the spacers 180, 182 (STEP 913), as shown in FIG. 13.

In accordance with one embodiment of the present invention, the spacers180, 182 are removed by another selective removal process (STEP 915), asshown in FIG. 14. For example, oxide spacers may be removed by anetching process in which any conventional etching agent is applied. Oncethe spacers 180, 182 have been removed, a second insulating layer ofinsulating material is applied (STEP 917), as shown in FIG. 15. Thesecond layer of applied insulating material fills the gaps left betweenthe first magnetic shield when the spacers 180, 182 were removed.Alternatively, the spacers 180, 182 may remain, and the second layer ofinsulation applied over the magnetic shield 113, the two parasiticshields 124, and the spacers 180, 182. In either case, the second layerof applied insulating material preferably becomes a contiguous part ofthe insulator 117. Next, the sensor element 111 is applied upon theinsulator 117 (STEP 919) and a third layer of insulating material isapplied over the sensor element 111 (STEP 921), as shown in FIG. 16.

The process used to form the spacers 180, 182 is then preferablyrepeated to form two additional spacers which are used in the mannerdescribed above to form a second magnetic shield 115 and a third andfourth parasitic shield 124 (STEP 923), as shown in FIG. 6a.

In an alternative method, each parasitic shield 124 and the firstmagnetic shield 113 are formed as a single structure. Two dividing linesare then etched through the structure to separate the structure into thefirst magnetic shield 113 and each parasitic shield 124. A secondinsulating layer is then applied over the parasitic shields 124 and themagnetic shield 113. The sensor element is then formed in the mannerdescribed above. Next, the second shield 115 and the associatedparasitic shields 124 are formed as a single structure. The structure isthen divided by etching two lines through the structure to form the gapbetween the second magnetic shield 115 and the third and fourthparasitic shields 124.

In yet another alternative embodiment, the spacers 180, 182 may beformed by etching three recesses in the insulating material, leaving afirst spacer 180 between the first and second recess, and leaving asecond spacer 182 between the second and third recess. Except for themanner in which the spacers are formed, the remainder of the method isthe same as the method shown in FIGS. 9a and 9b.

FIG. 17 is an illustration of a second embodiment of the presentinvention. In accordance with the second embodiment of the presentinvention, the proximal end 200, 204 of a first and second spark gapdevice 205, 203 are preferably directly electrically coupled to thefirst and the second magnetic shields 201, 202 respectively. The distalend 206 of each spark gap device 203, 205 is routed to come into closeproximity with the substrate 207. The proximal end 211 of a spark gapdevice 208 is coupled to the sensor 213. The distal end 215 of the sparkgap device 208 is routed to come into close proximity with the substrate207. Alternatively, the proximal end 200, 204, 211 of one or more of thespark gap devices may be in close proximity, but not in contact, withthe sensor 213 or the magnetic shield, respectively, and the distal end215 may be in direct electrical contact with the substrate 207.

In one embodiment of the present invention, shown in FIG. 18a, aconductive stud 210 extends preferably normal to the interface betweenthe substrate 207 and insulator 209. The stud 210 is electricallycoupled to the substrate 207. The proximal end 200, 211 of spark gapdevices 203', 205', 208' are coupled to the sensor element 213, thefirst magnetic shield 201 or the second magnetic shield 202,respectively. FIG. 18b is a cross-sectional view of the presentinvention taken along the line 18b--18b shown in FIG. 18a. The spark gapdevice 205' is shown to have HEFDI structures which increase theelectric field strength at the gap between the spark gap device 205' andthe stud 210. Accordingly, a sparkover will occur at a lower voltagedifference between the spark gap device 205' and the stud 210. The HEFDIstructures can be formed using conventional thin film depositiontechniques.

In one embodiment of the present invention, shown in FIG. 19, sensorleads (not shown) electrically couple the sensor element 213 to sensorpads 172 located at the deposition end 121' of the read head 107'. Thesensor pads 172 allow the sensor element to be connected to externalcircuitry. In the embodiment of the present invention shown in FIG. 19,the proximal end of a spark gap device 173 is coupled to the pad 172.The distal end of the spark gap device 173 includes HEFDI structures 175which are placed in close proximity to the stud 210. In an alternativeembodiment, the HEFDI structures 175 are placed in close proximity tothe substrate.

FIG. 20 is a deposition end view of another embodiment of the presentinvention in which each shield 201, 202 is also electrically coupled toa pad 230 at the deposition end 121' of a read head in similar fashionto the sensor element 213. Additional spark gap devices 232 may becoupled to each of the pads 230. Each spark gap device preferably hasHEFDI structures to increase the strength of the electric field at thegap between the spark gap device and the stud 210.

Each spark gap device 203', 205', 208' is preferably coplanar with thestructure to which that spark gap device 203', 205', 208' is coupled.For example, the spark gap device 208' is coplanar with the sensorelement 213, such that both the sensor element 213 and the spark gapdevice 208' can be applied in one process. It will be understood bythose skilled in the art that the relative location of the stud 210 isnot limited by the particular locations shown in FIG. 18a. Rather, thestud 210 may be located anywhere within the insulator 209 as long as thestud may be placed in direct electrical contact with the substrate 207,and each spark gap device 203', 205', 208' can be brought into closeproximity with the stud 210.

FIG. 21a and 21b are flowcharts of the method of fabricating the readhead of

FIG. 18a in accordance with one embodiment of the present invention. Afirst layer of an insulator 209, such as alumina, is applied to adeposition end, such as by being deposited on the deposition end of thesubstrate (STEP 2101). Alternatively, the insulator 209 may be appliedby any well-known technique, such as sputtering an insulting material,such as alumina on the substrate 207, introducing a liquid polymer ontothe wafer and spinning the wafer to distribute the polymer, ordepositing the insulating material by a chemical vapor deposition (CVD)technique. Next, at least a portion of a first shield 201 is depositedover the insulating material (STEP 2103). The first spark gap device203' is then applied to the substrate 209 (STEP 2105). In an alternativeembodiment, the spark gap device 203' is applied before the first shield201. It will be understood by those skilled in the art that the sparkgap device 203' may be deposited as a thinner element than the shield201. A second layer of insulating material 209 is then applied over thespark gap device 203' and the first shield 201 (STEP 2106). Next, thesensor element 213 is applied over the insulating material 209 (STEP2107). The second spark gap device 208' is then applied to theinsulating material 209 (STEP 2109). Alternatively, the spark gap device208' is applied before the sensor element 213.

A third layer of insulating material is then applied over the spark gapdevice 208' and the sensor element 213 (STEP 2111). A second shield 202is then applied over the insulating material 209 (STEP 2113) The thirdspark gap device 205' is then applied over the insulating material 209(STEP 2115). In an alternative embodiment, the spark gap device 205' isapplied before the second shield 202. Next, a fourth layer of insulatingmaterial 209 is applied over the second shield 202 and the spark gapdevice 205' (STEP 2117).

Next, a hole is formed through the insulating material (STEP 2119) inclose proximity to the distal ends of the spark gap devices 203', 208',205'. In one embodiment, the hole is chemically etched through thealumina in known fashion. Alternatively, the hole is formed by wellknown reactive ion techniques for selectively removing material. Oncethe hole is formed, the hole is filed with a conductive material to formthe stud 210 (STEP 2121).

The method for fabricating the embodiment shown in FIG. 20 is similar.However, the spark gap devices are not formed until after the stud 210has been formed. The spark gap devices 203', 205', 208' are applied tothe top layer of the insulating material 209. In addition, the pads 230,172 are formed in contact with conductive connections to each shield201, 202 and the sensor 213, in known fashion. The spark gap devices203', 205', 208' are formed in contact with an associated pad 230, 174and formed with an HEFDI structure in close proximity of the stud 210.

An important aspect of the present invention is the particular geometricconfiguration of the distal ends 215, 206 of the spark gap devices 203,203', 205, 205', 208, 208'. Since the gap between sensor element 213 andthe magnetic shields 201, 202 is as small as 0.12 μm, it would be verydifficult to fabricate a gap between a spark gap device 203, 203', 205,205', 208, 208' that is smaller than 0.12 gap μm. Therefore, in order toensure that the sparkover between the sensor element 213 and themagnetic shield 201, 202 does not occur before a sparkover between thesensor element 213 and the substrate through the spark gap device 208,208', the distal end 215 of the spark gap device 208, 208' must havefeatures that concentrate the electric field. That is, by fabricatingthe distal end 215 of the spark gap device 208, 208' to have generallypointed structures (i.e., structures preferably having a radius of lessthan about 1 μm), the electric field that is generated by the differencein potential between the substrate 207 and the distal end of the sparkgap device 208, 208' is concentrated in a relatively smaller area. Itwill be understood by those skilled in the art that the radius may begreater than 1 μm. However, the greater the radius, the lessconcentrated the charge. Such concentration of the electric field in theinsulator 209 will ensure that the sparkover occurs between the sparkgap device 208, 208' at a lower electrical potential than is requiredfor a sparkover between one of the magnetic shields 113, 115 and thesensor element 111, or between one of the magnetic shields 113, 115 andthe substrate.

A number of embodiments of the present invention have been described.However, it should be understood that each described embodiment ismerely intended to serve as an examplar, and is not intended to limitthe scope of protection provided. Accordingly, only those limitationsspecified in the accompanying claims shall be used to define and limitthe scope of the present invention. A number of additional variationsmay be made to the present invention without departing from the presentinvention. For example, a wide variety of materials may be used tofabricate the substrate, the magnetic shield, and the sensor element.Furthermore, any particular shape may be used at the distal end of thespark gap devices defined by the present invention. Also, a number ofdifferent general configurations may be used in which the relativeposition of the components of a read head are varied. That is, one ormore magnetic shields may be curved to wrap around the sensor element.The particular shape of the sensor element may vary from that shown inthe accompanying figures. Furthermore, each spark gap device may makecontact with each element of the read head at any point of contact.Still further, each spark gap device may follow any conductive path.Furthermore, the stud may be formed from any essentially conductivematerial. With respect to the embodiment of the present invention inwhich parasitic shields are provided, a number of methods have beendescribed above for fabricating a read head with parasitic shields.However, a number of alternative methods exist for fabricating suchparasitic shields. It should be clear that any of these methods wouldfall within the scope of the invention described in the presentdisclosure. Also, while the present invention is described generally inthe context of a slider, it will be understood that a read head may beinstalled or fabricated upon a variety of platforms. Still further, thepresent invention is described in the context of a read head only forease of understanding. However, the present invention is applicable toany device which requires protection from electrostatic dischargebetween components that are not electrically coupled, but which are soclose that a sparkover may occur between the components at relativelylow voltages due to contact of one component with a charged body whichtransfers charge to that component. Accordingly, the present inventionis not to be limited by the particular embodiments that are disclosedherein, but rather by the recitation of the following claims.

We claim:
 1. A read head protection circuit, for discharging electriccharges accumulated on a component of a read head, the read head havingat least a substrate, at least one magnetic shield and at least onesensor element, including: at least one spark gap device, having aproximal end electrically coupled to the magnetic shield, and a distalend formed in close proximity to the substrate.
 2. The read headprotection circuit of claim 1, wherein the distal end of at least one ofthe at least one spark gap devices has at least one high electric fielddensity inducing device.
 3. The read head protection circuit of claim 1,wherein the proximal end of at least one of the at least one spark gapdevices is coupled to the sensor element.
 4. A read head protectioncircuit, for discharging electric charges accumulated on a component ofa read head, the read head having at least a substrate, at least onemagnetic shield and at least one sensor element, the read headprotection circuit including:at least one electrically conductive studcoupled to the substrate; at least one spark gap device, having aproximal end electrically coupled to the magnetic shield, and a distalend formed in close proximity to at least one of the studs.
 5. The readhead protection circuit of claim 4, wherein the distal end of at leastone of the spark gap devices includes at least one high electric fielddensity inducing device.
 6. The read head protection circuit of claim 4,wherein the proximal end of at least one of the spark gap devices iscoupled to the sensor element.
 7. A read head protection circuit fordischarging electric charges accumulated on a component of a read head,comprising:a substrate; a pair of magnetic shields supported on thesubstrate; a sensor element positioned between the magnetic shields,there being fixed distances between the sensor element and the magneticshields; for each magnetic shield, a corresponding parasitic shieldpositioned adjacent the magnetic shield nearer to the magnetic shieldthan the fixed distance between the magnetic shield and the sensorelement.
 8. The read head protection circuit of claim 7, furtherincluding an electrostatic discharge circuit between the magnetic shieldand one of the parasitic shields.
 9. The read head protection circuit ofclaim 8, the electrostatic discharge circuit comprising an activedevice.
 10. The read head protection circuit of claim 9, the activedevice circuit comprising a transistor.
 11. The read head protectioncircuit of claim 8, the electrostatic discharge circuit comprising apassive device.
 12. The read head protection circuit of claim 7, eachparasitic shield having a region nearest the corresponding magneticshield, the regions defining pointed spark gap inducing structures. 13.The read head protection circuit of claim 7, further comprising:means tomaintain each parasitic shield substantially at an electrical potentialof the sensor element.
 14. A read head protection circuit fordischarging electric charges accumulated on a component of a read head,comprising:a substrate; a pair of magnetic shields supported on thesubstrate; a sensor element positioned between the magnetic shields; andmeans to maintain the sensor element substantially at an electricalpotential of at least one of the magnetic shields with respect to apredetermined reference potential.
 15. The read head protection circuitof claim 14, the means comprising a conductive structure.
 16. The readhead protection circuit of claim 15, the conductive structurecomprising:a first spark gap device electrically coupled to the sensorelement and extending therefrom to a first tip having close proximity tothe substrate; and one or more second spark gap devices electricallycoupled to one or more of the magnetic shields and extending therefromto a corresponding number of second tips having close proximity to thesubstrate.
 17. The read head protection circuit of claim 16, each of thefirst and second tips defining pointed spark gap inducing devices. 18.The read head protection circuit of claim 14, the conductive structurecomprising:a conductive stud coupled to the substrate and extendingtherefrom; and spark gap devices extending from the sensor element andat least one magnetic shield into close proximity with the stud.
 19. Aread head protection circuit for discharging electric chargesaccumulated on a component of a read head, comprising:a substrate; apair of magnetic shields supported on the substrate; a sensor elementpositioned between the magnetic shields; and a conductive structure tomaintain the sensor element substantially at an electrical potential ofat least one of the magnetic shields; wherein an electrical potentialrequired to cause a sparkover between either of the magnetic shields andthe sensor element is greater than an electrical potential required tocause a sparkover between either of the parasitic shields and theadjacent magnetic shield.